Interlaced magnetic recording band isolation

ABSTRACT

Methods and apparatus for allocating logical sectors and bands to store data on interlaced magnetic recording tracks. The systems and methods include formatting a data storage medium to include a plurality of bands, each band of the plurality of bands including a plurality of tracks, the plurality of tracks including a subset of top tracks interlaced with a subset of bottom tracks, and each track of the plurality of tracks including a number of sectors, formatting a first band of the plurality of bands, determining an isolation region of the first band, and formatting a second band of the plurality of bands responsive to determining the isolation region of the first band.

CROSS-REFERENCE

This application is a divisional application of U.S. patent applicationSer. No. 16/256,860 filed Jan. 24, 2019 and titled INTERLACED MAGNETICRECORDING BAND ISOLATION, the entire disclosure of which is incorporatedherein by reference for all purposes.

BACKGROUND

Interlaced magnetic recording (IMR) generally refers to the concept ofutilizing two or more selected written track widths and two or moredifferent linear densities for data writes to alternating data tracks ona storage medium. In these systems, data tracks may be read from orwritten to the data tracks in a non-consecutive order. For example, datamay be written exclusively to a first track series including every otherdata track in a region of a storage medium before data is written to anydata tracks interlaced between the tracks of the first series.

SUMMARY

Systems and methods are disclosed for allocating logical sectors tostore interlaced magnetic recording (IMR) bands. The systems and methodsinclude formatting a data storage medium to include a plurality ofbands, each band of the plurality of bands including a plurality oftracks, the plurality of tracks including a subset of top tracksinterlaced with a subset of bottom tracks, and each track of theplurality of tracks including a number of sectors, formatting a firstband of the plurality of bands, determining an isolation region of thefirst band, and formatting a second or next band of the plurality ofbands responsive to determining the isolation region of the first band.The formatting of the band and determination of the isolation region isaccomplished via an iterative supposition process.

In one particular implementation, a method for formatting a data storagemedium to include a plurality of bands with an isolation region betweenadjacent bands, each band comprising a plurality of tracks, theplurality of tracks comprising a subset of top tracks interlaced with asubset of bottom tracks, and each track comprising a number of sectors,is provided. The method includes formatting a preliminary bandcomprising a number of sectors such that the subset of bottom tracks areconfigured to store data and none of the subset of top tracks areconfigured to store data. The preliminary band is iterativelyreformatted such that the subset of bottom tracks is configured to storeone fewer sectors than a prior iteration of the preliminary band, andthe subset of top tracks is configured to store one sector further thanthe prior iteration of the preliminary band, the number of sectorsconfigured to store data in the band being kept constant, whereiniteratively reformatting comprises discarding from the preliminary bandany bottom track no longer intended to store data. After iterativelyreformatting, finalizing the format of the band when an isolation region(a region prior to the start of the next band where no data is to bestored) can be formatted comprising no more than one entire track orcircumferentially complementary portions of two adjacent tracks. In someimplementations, the bottom and top tracks configured to store data mayalso be characterized as being planned to store data, meaning that isthe intention of the method at the time of formatting.

In another particular implementation, a method for formatting a datastorage medium to include a plurality of bands with an isolation regionbetween adjacent bands, each band comprising a plurality of tracks, theplurality of tracks comprising a subset of top tracks interlaced with asubset of bottom tracks, and each track comprising a number of sectors,is provided. This method includes filling the subset of bottom trackswith data, iteratively moving data from a sector of the subset of bottomtracks to a sector of the subset of top tracks, until the number ofempty top tracks inward from the end non-empty bottom track is zero; andassigning an isolation region responsive to a determination if thesubset of bottom tracks has a non-full track, assigning that portion ofthe non-full track as a first portion of the isolation region, andassigning a corresponding portion of an adjacent top track as a secondportion of the isolation region, or if the subset of bottom tracks doesnot have a non-full track, assigning no more than an entire adjacent toptrack as the isolation region.

The disclosure provides formatting a first IMR band such that, at anextreme, an isolation region can be formatted comprising of a full trackor circumferentially complementary portions of adjacent tracks (e.g.,top/bottom or bottom/top), and responsive to formatting the first bandand the isolation region, formatting a subsequent IMR band. Theiterative supposition (1) provides a framework to prove that an IMR bandcan be formatted from nonzero-sized IMR tracks with an end-mostconfiguration satisfying specific configurations, and (2) providing analgorithm for formatting the IMR band. It should be understood that whendiscussion is made regarding filling tracks and iteratively moving data,that actual data may not be written and/or moved, but that the processof writing and moving data is theoretical.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. These andvarious other features and advantages will be apparent from a reading ofthe following Detailed Description.

BRIEF DESCRIPTIONS OF THE DRAWING

The described technology is best understood from the following DetailedDescription describing various implementations read in connection withthe accompanying drawing.

FIG. 1A is a schematic plan view of an example disc drive assembly; FIG.1B is a plan view of an enlarged portion of the example disc driveassembly showing a plurality of interlaced magnetic recording (IMR)tracks; FIG. 1C is a schematic side view of the enlarged portion of theexample disc drive assembly showing the plurality of IMR tracks.

FIGS. 2A, 2B and 2C are schematic side views of a plurality of IMRtracks showing steps in an iterative supposition process.

FIGS. 3A, 3B and 3C are three schematic side views of a plurality of IMRtracks showing N=3, N=2, and N=0, respectively.

FIGS. 4A, 4B, 4C, 4D, 4E and 4F are six schematic side views of aplurality of IMR tracks.

FIG. 5A is a schematic side view of an IMR band arrangement with a trackas an isolation region; FIG. 5B is a schematic side view of an IMR bandarrangement with circumferentially complementary portions of twoadjacent tracks as an isolation region.

FIG. 6 is a logical flowchart of an iterative supposition process.

FIG. 7 is a flowchart of a general process for formatting an IMR system.

FIG. 8 is a flowchart of example operations for allocating logicalsectors to IMR bands via an iterative supposition process.

FIG. 9 is a flowchart of example operations for allocating logicalsectors to IMR bands via an iterative supposition process.

FIG. 10 is a block diagram of a computer system in a data storagesystem.

DETAILED DESCRIPTION

As requirements for area storage density increase for magnetic media,cell size decreases. A commensurate decrease in the size of a writeelement is difficult because in many systems, a strong write field isneeded to shift the polarity of cells on a magnetized medium. As aresult, writing data to smaller cells on the magnetized medium using therelatively larger write pole may affect the polarization of adjacentcells (e.g., overwriting the adjacent cells). One technique for adaptingthe magnetic medium to utilize smaller cells while preventing adjacentdata from being overwritten during a write operation is interlacedmagnetic recording (IMR).

As explained in further detail with reference to the various figuresbelow, IMR systems may utilize two or more selected written track widthsand two or more different linear densities for data writes toalternating data tracks on a storage medium. In these systems, datatracks may be read from or written to the data tracks in anon-consecutive order. For example, data may be written exclusively to afirst track series including every other data track in a region of astorage medium before data is written to any data tracks interlacedbetween the tracks of the first series.

In IMR systems, a data track of wide written track width is writtenprior to directly adjacent data tracks of narrower written track width.The data tracks of the wider written track width are also referred toherein as “bottom tracks,” while the alternating data tracks of narrowerwritten width are referred to herein as “top tracks.” In someimplementations, the bottom tracks of wider written track width includedata stored at a different linear density than one or more top tracks ofnarrow written track width. In still other implementations, the bottomand top data tracks are of equal written track width.

IMR can allow for significantly higher areal recording densities thanmany existing data management systems. However, effective IMR systemsare designed to implement prioritized write access rules that can, insome implementations, entail significant read/write overhead. Forinstance, modifying a target data track in an IMR system may entailreading two or more adjacent top tracks into memory, modifying thetarget bottom track, and re-writing the two or more adjacent top tracks.

As described in more detail below with respect to the figures, inhost-managed IMR and drive-managed IMR, it is advantageous to haveindividually rewritable IMR bands of a logically uniform size withminimum overprovisioning for isolation of the bands one from another.The herein disclosed technology includes allocating the logical sectorsneeded to store an IMR band, possibly of a specific, possibly of auniform logical size, to variably-sized IMR tracks at a locality on thesurface of a storage media.

Specifically, the disclosed technology is directed toward achievingisolation of IMR bands at an overprovisioning cost of one track's worthof sectors per iso-band, where a plausible worst case for that tracksize (e.g., considering a track's worth of sectors) being that of abottom track in the region of the IMR band (e.g., the bottom trackshaving more sectors per track on average than the top tracks).

For purposes of this disclosure, the disclosed technology is describedin an IMR data storage system. Other storage systems are contemplated,e.g., a perpendicular IMR system, a heat-assisted IMR system (HIMR),etc.

In the following description, reference is made to the accompanyingdrawing that forms a part hereof and in which is shown by way ofillustration at least one specific implementation. The followingdescription provides additional specific implementations. It is to beunderstood that other implementations are contemplated and may be madewithout departing from the scope or spirit of the present disclosure.The following detailed description, therefore, is not to be taken in alimiting sense. While the present disclosure is not so limited, anappreciation of various aspects of the disclosure will be gained througha discussion of the examples, including the figures, provided below. Insome instances, a reference numeral may have an associated sub-labelconsisting of a lower-case letter to denote one of multiple similarcomponents. When reference is made to a reference numeral withoutspecification of a sub-label, the reference is intended to refer to allsuch multiple similar components.

FIG. 1A illustrates in plan view of an example disc drive assembly 100that includes a magnetic storage medium 102 and a transducer headassembly 120 with a writer and reader (not shown) for writing andreading data to and from the magnetic storage medium 102. The transducerhead assembly 120 may include any of a number of reader and writerconfigurations such as HAMR (Heat-Assisted Magnetic Recording), multipleread and/or write heads, etc. Although other implementations arecontemplated, the magnetic storage medium 102 is, in FIG. 1A, a magneticstorage disc on which data bits can be recorded using a magnetic writepole and from which data bits can be read using a magnetoresistiveelement (not shown). As illustrated in FIG. 1A, the magnetic storagemedium 102 has an inner diameter 104 and an outer diameter 108 betweenwhich are a number of concentric data tracks 110. The medium 102 rotatesabout a spindle center or a disc axis of rotation 105. Information maybe written to and read from data bit locations in the data tracks 110 asthe magnetic storage medium 102 rotates.

The magnetic storage medium 102 includes a number of servo sectors 112extending radially between the inner diameter 104 and the outer diameter108; five servo sectors are illustrated in FIG. 1A. In oneimplementation, each of the servo sectors 112 includes embeddedinformation used for track seeking and track following, such as finehead position information used for centerline tracking. Between everytwo consecutive servo sectors 112 is a wedge 114 that includes multiplesectors (e.g., data sectors and super parity sectors, not shown) ofconcentric data tracks 110.

The transducer head assembly 120 is mounted on an actuator assembly 109at an end distal to an actuator axis of rotation 103. The transducerhead assembly 120 flies in close proximity above the surface of themagnetic storage medium 102 during disc rotation. The actuator assembly109 rotates or pivots during a seek operation about the actuator axis ofrotation 103 to position the transducer head assembly 120 over a targetdata track 110 during read and write operations.

The disc drive assembly 100 further includes a storage controller 106.The storage controller 106 includes software and/or hardware and may beimplemented in any tangible processor-readable storage media within orcommunicatively coupled to the disc drive assembly 100, particularly, tothe actuator assembly 109. The term “tangible processor-readable storagemedia” includes, but is not limited to, RAM, ROM EEPROM, flash memory orother memory technology, CDROM, digital versatile discs (DVD) or otheroptical disc storage, magnetic cassettes, magnetic tape, magnetic discstorage or other magnetic storage devices, or any other tangible mediumwhich can be used to store the desired information and which can beaccessed by a processor. In contrast to tangible processor-readablestorage media, intangible processor readable communication signals mayembody processor readable instructions, data structures, program modulesor other data resident in a modulated data signal, such as a carrierwave or other signal transport mechanism. The term “modulated datasignal” means a signal that has one or more of its characteristics setor changed in such a manner as to encode information in the signal. Insome implementations, a look-up table may be included in a read/writesubsystem to locate a starting track of each band.

FIG. 1B illustrates a magnified view of a section of the data tracks 110of the magnetic storage medium 102. FIG. 1B illustrates multiple datatracks 130, 131, 132, 133, 134 intended to store data according to aninterlaced magnetic recording (IMR) configuration or technique. The datatracks 130, 131, 132, 133, 134 are each divided into data sectors (e.g.,data sectors 180, 181, 182, 183, 184, respectively) which include aplurality of polarized regions (not shown), also referred to as “databits,” each representing one or more individual data bits of the samestate (e.g., is or Os).

The illustrated IMR technique utilizes alternating data tracks ofdifferent written track widths arranged with slightly overlappingwritten track boundaries so that a center-to-center distance betweendirectly adjacent tracks (e.g., the track pitch) is uniform across anarea (e.g., a radial zone or across an entire surface of the magneticstorage medium 102). Specifically, FIG. 1B illustrates a first series ofalternating tracks (e.g., the tracks 131 and 133) with a wider writtentrack width than a second series of alternating data tracks (e.g., thetracks 130, 132, and 134). The first series of alternating tracks arereferred to as “bottom tracks”, and the second series of alternatingtracks are referred to as “top tracks;” in another way, the wideralternating tracks are referred to as “bottom tracks” and the narrowalternating tracks are referred to as “top tracks.” FIG. 1C illustratesthe tracks 131, 133 as “bottom tracks” and the tracks 130, 132, 134 as“top tracks”.

Typically, each wide data track (bottom track) of a series of tracks iswritten before any directly-adjacent data track (top track) of thesecond series is written. For example, the data track 131 is writtenbefore either of the data tracks 130 and 132 is written. Datasubsequently written to the data tracks 130 and 132 may overwrite theouter edge portions of the previously-written data track 131; however,the data track 131 is still readable due to sufficient informationretained in a center region of the data track 131.

One consequence of IMR is that a bottom track (e.g., a data track 131)is not randomly writable when data is stored on a directly adjacent topdata track (e.g., the data track 130 or 132). As used herein, a datatrack is “randomly writable” when the data track can be individuallyre-written multiple times without significantly degrading data on otheradjacent data tracks. An adjacent data track is “significantly degraded”if reading the data track results in a number of read errors in excessof a maximum number of errors that can be corrected by an errorcorrection code (ECC) of the disc drive assembly 100.

Top tracks (e.g., data tracks 130, 132, 134) are generally randomlywritable because they can be individually rewritten without degradingdata on adjacent (bottom) data tracks (e.g., tracks 131, 133). However,some implementations of IMR systems have issues with servo write offtrack (SWOT), meaning that the write head of the transducer head 120writes off center of the target track and into an adjacent trackresulting in a degradation of the data on the adjacent track. Forexample, if transducer head 120 is writing on top track 132 it may writeoff center of the top track 132 (e.g., toward the bottom track 131),which may degrade the data on the bottom track 131. When the transducerhead 120 suffers from SWOT such as in the example described above, itmay not have an effect on the opposing top track (e.g., the top track130). Only the adjacent bottom track 131 may be affected. For a giventrack spacing, it may not be safe to overwrite top track sectors morethan once due to the incremental risk of impacting the bottom tracks. Insome implementations, the risk of detrimental impact to the bottomtracks is tolerable for one write but is typically not tolerable formore than one top track overwrite.

A set of tracks (e.g., tracks 130, 131, 132, 133, 134) may be groupedinto a “band,” with the band having a guard track or portion(s) oftrack(s) that isolates the band from the next group of tracks or nextband; for example, a guard track (not shown in FIG. 1) may be presentadjacent to track 130 and/or track 134. A guard track or portion(s) oftrack(s) can be also referred to as an “isolation track,” and isdesignated as not to be written. The isolation track provides bandboundaries to separate writable tracks of different bands and to guardthe last track of a band. Drive managed and host managed IMR separatesbands with guard tracks so that rewriting a track in the band does notrequire rewriting tracks outside that band.

The disc space allotted for a band may be chosen before the disc spacefor a subsequent and/or adjacent band is chosen. The allocation of discspace for a band can depend on the sectors (e.g., sectors 181, 183) ofthe track(s) (e.g., tracks 131, 133) under consideration. The numberand/or size of sectors per track can vary between the bottom tracks andthe top tracks; media variations (e.g., variable bit aspect ratio) canalso vary between the bottom tracks and the top tracks. On average,bottom tracks have more sectors per track than top tracks. However, insome implementations, the number of sectors per track also varies basedon defects in the band, track or sectors.

The technology described herein includes allocating the sectors to storean IMR band (e.g., 256 MiB of data) to the variably sized IMR tracks atthat locality on the surface of the magnetic storage medium 102. In anideal situation, a band fills an entire track length, leaving theadjacent track as an isolation or guard track. However, bands may startand end at radially varying locations on the medium 102 such that thelast track (in a band) is not necessarily a full track. Instead, apartial last or end track (e.g., “rightmost” end track) is either apartial top track or a partial bottom track. In such a scenario, the endpartially full track is “spooned” together with the adjacent, alternatetype of track (e.g., bottom-top or top-bottom). These two partial tracksare then designated as the isolation or guard region. The specific andoptimal location of these isolation or guard regions, whether a fulltrack or partial tracks forming a region, can be determined by iterativesupposition.

The iterative supposition process, to determine the location ofisolation or guard regions for an IMR technique, as per this disclosure,iteratively moves representations of data (e.g., 256 MiB of data) toform a consolidated band, taking into account defective and otherwiseunusable sectors. The iterative supposition process involves no writingof actual data, but moving representative data to reach a finalassignment of sectors to tracks to form the band. The iterativesupposition accounts for variation in the sectors size, numbers ofsectors, defects in the sectors, etc.; thus, each resulting consolidatedband is optimized. There may be variably sized tracks in a band, withdifferent numbers of sectors on each track.

To begin the iterative supposition process, a series of tracks (e.g.,bottom tracks) is theoretically filled with one band of data (e.g., 256MiB). FIG. 2A illustrates a preliminary configuration 200 having aseries of tracks 202 (particularly, tracks 202 a, 202 b, 202 c, 202 d,202 e, 202 f, 202 g, 202 h) that together have one band of (theoretical)data therein. The tracks 202 a, 202 b, 202 c, 202 d, 202 e, 202 f, 202 gare full tracks (e.g., all the sectors are full) whereas the track 202 h(shown with crosshatch) is only partially full. A second series oftracks 204 (e.g., top tracks), particularly, tracks 204 a, 204 b, 204 c,. . . are shown in phantom, but no data is provided to those tracks 204initially. As illustrated, the first series of tracks 202 are bottomtracks, and the second series of tracks 204 are top tracks.

FIG. 2B illustrates a step of the iterative supposition process,beginning with the preliminary, theoretical data configuration of FIG.2A and leading to a final IMR band. In this supposition step, one sectoris shifted at a time from the last or end bottom track to the last orend available top track, in an incremental supposition. FIG. 2B,specifically, shows top track 204 a, which was empty in FIG. 2A, beingfilled, sector by sector, from bottom track 202 h.

FIG. 2C shows a later intermediate step of the iterative suppositionprocess, where a sufficient number of iterative steps have occurred sothat bottom tracks 202 h and 202 g are empty, bottom track 202 f ispartially full, top tracks 204 a and 204 b are full, and top track 204 cis partially full.

The iterative supposition process drains the bottom tracks (e.g., tracks202) and fills the top tracks (e.g., tracks 204). Although the iterativesupposition ends (as discussed later) with a completed band layout witha completed and condensed allocation of sectors to both the bottom andtop tracks, one or both of the end tracks (e.g., rightmost top track,rightmost bottom track) may be partially full. In other implementations,the end track(s) may not be partially full, but be completely full. Atrack that is partially full may have, e.g., only one sector that isfull and the rest of the sectors empty, or only one sector empty and therest of the sectors full, or any empty/full distribution.

During the iterative supposition process, there is a track number “N”which is the number of empty top tracks inward from the end non-emptybottom track (e.g., the number of empty top tracks to the left of therightmost non-empty bottom track). FIGS. 3A, 3B and 3C show layoutswhere N=3, N=2 and N=0, respectively. In these figures, the bottomtracks are identified generally as tracks 302 and the top tracks areidentified generally as tracks 304.

In FIG. 3A specifically, the configuration 300A has bottom tracks 302 a,302 b, 302 c, 302 d that are full tracks and top tracks 304 a, 304 b,304 c that are empty. There are three empty top tracks from the endnon-empty bottom track, so that N=3.

In FIG. 3B specifically, the configuration 300B has bottom tracks 302 a,302 b, 302 c, 302 d, 302 e that are full tracks, bottom track 302 f ispartially full, top tracks 304 a, 304 b are full, and top track 304 c ispartially full. Top tracks 304 d, 304 e are empty. There are two emptytop tracks from the end non-empty bottom track, so that N=2.

In FIG. 3C specifically, the configuration 300C has bottom tracks 302 a,302 b, 302 c, 302 d that are full tracks, bottom track 302 e ispartially full, and top tracks 304 a, 304 b, 304 c, 304 d are full.There are no empty top tracks from the end non-empty bottom track, sothat N=0.

In some implementations, at the beginning of the iterative suppositionprocess, as shown in FIG. 2A, N is at least 3, in some implementationsat least 4, due to the number of tracks in a series (e.g., bottom levelof tracks) needed for one band of data. FIG. 2A actually shows N=7.

During the iterative supposition process, a shift of a single sectorfrom a bottom track to a top track will decrease N by 0 (zero), 1 or 2.For example, if as a result of a sector shift the endmost bottom trackis emptied but the endmost top track remains partially full, N hasdecreased by 1. As another example, if as a result of a sector shift theendmost bottom track remains partially full and the endmost top track isstarted (and is now partially full), N has decreased by 1. As anotherexample, if as a result of a sector shift the endmost bottom track isemptied and the endmost top track is started, N has decreased by 2. Inall implementations, after each iteration, the bottom tracks have oneless sector and the top tracks have one more sector; in other words, onesector is shifted in each iteration. Continued iterative suppositionwill arrive at a completed band as described below.

FIGS. 4A, 4B, 4C, 4D, 4E and 4F illustrate four examples where N=0 (FIG.4A, FIG. 4B, FIG. 4E, and FIG. 4F), and two examples where N is negative1 (FIG. 4C and FIG. 4D). In all these examples, the endmost top trackand the endmost bottom track are both non-empty (e.g., full or partiallyfull).

FIG. 4A illustrates a configuration 400A where the endmost bottom track402 x is full and the endmost top track 404 x is full. Thisconfiguration 400A can also be referred to as “Case #1.”

FIG. 4B illustrates a configuration 400B where the endmost bottom track402 x is partially full and the endmost top track 404 x is full. Thisconfiguration 400B can also be referred to as “Case #2.”

FIG. 4C illustrates a configuration 400C which is configuration 400Aflipped. where the endmost bottom track 402 x is full and the endmosttop track 404 x is full. This configuration 400C can also be referred toas “Case #3.”

FIG. 4D illustrates a configuration 400D the endmost bottom track 402 xis partially full and the endmost top track 404 x is full, which isconfiguration 400B flipped. This configuration 400D can also be referredto as “Case #4.”

FIG. 4E illustrates a configuration 400E where the endmost bottom track402 x is full and the endmost top track 404 x is partially full.

FIG. 4F illustrates a configuration 400F where both the endmost bottomtrack 402 x and the endmost top track 404 x are partially full.

Although the configuration 400E of FIG. 4E and the configuration 400F ofFIG. 4F have N=0, the iterative supposition process can be continued onthese configurations to eventually arrive at one of the configurationsof FIG. 4A (Case #1), FIG. 4B (Case #2), FIG. 4C (Case #3) or FIG. 4D(Case #4).

After arriving at one of the configurations of FIG. 4A (Case #1), FIG.4B (Case #2), FIG. 4C (Case #3) or FIG. 4D (Case #4), the iterativesupposition is complete, the band has been consolidated, and thelocation of band boundary has been determined. The isolation region isthus assigned. Depending on the configuration of the band, the isolationregion may be a single track or may be a first portion on a first trackand a second portion on an adjacent track, the portions beingcircumferentially complementary. FIG. 5A illustrates an isolation orguard region formed by a full track between two adjacent bands based onthe configuration 400A of FIG. 4A. FIG. 5B illustrates an isolation orguard region between two circumferentially complementary portions ofadjacent tracks based on the configuration 400B of FIG. 4B.

In FIG. 5A, the configuration 500A has a band formed by bottom tracks502 a, 502 b, 502 c, 502 d and top tracks 504 a, 504 b, 504 c; all ofthese tracks 502 a, 502 b, 502 c, 502 d, 504 a, 504 b, 504 c are full.The next adjacent track, top track 504 d is empty, and is thusdesignated as an isolation or guard track 510A. The tracks 502 e, 504 eare the beginning of the next adjacent band.

In FIG. 5B, the configuration 500B has a band formed by full bottomtracks 502 a, 502 b, 502 c, 502 d, partially full bottom track 502 e,and full top tracks 504 a, 504 b, 504 c, 504 d. An isolation or guardtrack 510B is defined by the empty portion 512 of the bottom track 502 eand a sufficient portion 514 of the top track 504 e to form, with emptyportion 512, an isolation or guard region 510B that has approximatelythe same number of sectors as a full track. The next adjacent bandincludes part of the top track 504 e (the part that is not portion 514),bottom track 502 f, top track 504 f, and subsequent tracks.

The bands and the isolation or guard regions reflect the end result ofthe iterative supposition process. The resulting band is optimallyconsolidated, taking into account unusable sectors (e.g., defectivesectors), so that the location of the isolation region can bedetermined.

FIG. 6 shows a method 600, in stepwise manner, of the overall iterativesupposition process used to determine the area needed for a consolidatedband of data.

Initially, lower tracks of an IMR system are filled with one band'sworth of representative data (e.g., 256 MiB), as is shown in FIG. 2A. Inoperation 602 in FIG. 6, one sector is shifted from the endmost bottomtrack to the endmost top track. In operation 604, it is evaluatedwhether or not N=0 or N=1, where N= is the number of empty top tracksinward from the endmost non-empty bottom track. If N=0 or N=1, theprocess progresses to operation 606; if N is other than 0 or 1 (e.g.,N=2), return to operation 602 and continue shifting one sector from theendmost bottom track to the endmost top track.

From operation 606, if N=0 then progress to operation 608; at this step,if N=0 and the configuration is either Case #1 (FIG. 4A) or Case #2(FIG. 4B), then the iterative supposition is done, operation 610.However, if at operation 608, if both N=0 and the configuration iseither Case #1 (FIG. 4A) or Case #2 (FIG. 4B) are not true, then atoperation 612 it is determined whether the unshifted supposed sectorcontent in the endmost bottom track (B) is the same as the availablespace in the endmost top track (T). If yes, then progress to operation614 where iterative supposition continues shifting sectors from theendmost bottom track to supposedly empty the bottom track, until theiterative supposition is done at operation 624. This operation ischaracterized as supposedly empty because, as initiated above, the dataand movement of data during the process, in some implementations, can beconsidered theoretical. However, if at operation 612 it is determinedthe unshifted supposed sector content in the endmost bottom track (B) isnot the same as the available space in the endmost top track (T), thengo to operation 616, where it is determined whether the unshiftedsupposed sector content in the endmost bottom track (B) is more than theavailable space in the endmost top track (T). If yes, then go tooperation 618 where iterative supposition continues shifting sectorsfrom the endmost bottom track to fill the endmost top track, until theiterative supposition is done at operation 620.

If at operation 616 it is determined that the unshifted supposed sectorcontent in the endmost bottom track (B) is not more than the availablespace in the endmost top track (T), then progress to operation 614 whereiterative supposition continues shifting sectors from the endmost bottomtrack to empty the bottom track, until the iterative supposition is doneat operation 624.

Returning to operation 606, if N is not equal 0 then progress tooperation 626. At operation 626, if the next shift will leave N=1, thengo to operation 628 to continue shifting and return to operation 626until it is determined the next shift will not leave N=1; when thisoccurs, progress to operation 630. At operation 630, if the next shiftwill leave N=0, then shift one sector from the bottom to the top andprogress to operation 608, where it is evaluated if it is Case #1 (FIG.4A) or Case #2 (FIG. 4B). However, if at operation 630 the next shiftwill not leave N=0, then progress to operation 632 where iterativesupposition performs one final shift to finish at operation 634.

Referring to FIG. 7, a flowchart of operations for allocating disc spacein the storage medium by identifying a boundary of the first band andseparating writable tracks of different bands is provided. The process700 may comprise configuring a first band with a designated capacity(e.g., 256 MiB). The designated capacity may include an initial numberof non-defective sectors, to which may or may not be added one or twospare sectors or tracks, for example, to compensate for defectivesectors. The process 700 may include determining an adequate isolationregion. An adequate isolation region may be an amount of spacesufficient to prevent data recorded to one band from interfering withtracks of an adjacent band. An adequate isolation region may compriseone or more sectors to create a buffer between sectors of adjacentbands. The isolation region may comprise one or more whole, partiallyfilled, or fractional tracks.

In the process 700, an operation 702 formats a data storage medium toinclude a plurality of bands, each band of the plurality of bandsincluding a plurality of tracks, the plurality of tracks including asubset of top tracks interlaced with a subset of bottom tracks, and eachtrack of the plurality of tracks including a number of sectors. Anoperation 704 iteratively formats a Nth band of the plurality of bands,the Nth band occupying a number of top tracks and a number of bottomtracks. An operation 706 determines an isolation region adjacent to theNth band. At operation 708, if additional bands are to be iterativelyformatted adjacent to the determined isolation region, then return tooperation 704; if not, end at operation 710.

A flowchart of operations is shown in FIG. 8 as process 800; thisprocess 800 provides exemplary alternate details compared to theoperations 702, 704, 706 of the process 700. Particularly, FIG. 8 is aflowchart of example operations for allocating logical sectors to IMRbands via an iterative supposition process, stopping when an isolationregion can be formatted. Note that FIG. 6 is the specific guidance as towhen an isolation region can be formatted.

In an operation 802, a band is supposedly formatted, by filling bottomtracks and not interlaced top tracks. In an operation 804, the band fromthe operation 802 is reformatted, by iteratively storing one less sectorin the bottom tracks and one more sector in the top tracks. In anoperation 806, any empty bottom track is discarded from the band. Inoperation 808, the band is finalized when an isolation region can beformatted.

Subsequent to the operation 808, if another band is to be iterativelyformatted at operation 810, the process returns to the operation 802; ifnot, end at operation 812. In such a manner, an entire disc can beformatted with bands.

Another flowchart of operations is shown in FIG. 9 as process 900; thisprocess 900 provides other exemplary alternate details compared to theoperations 702, 704, 706 of the process 700.

In an operation 902, sectors of a series of bottom tracks are supposedlyfilled with one band of data. In an operation 904, individually, sectorsfrom the end bottom track are iteratively moved to the interlaced endtop track until there is one more non-empty bottom track than top track.The operation 904 thus results in a consolidated band. In an operation906, after determining the band in the operation 904, an isolationregion is assigned. If the end bottom track of the band is a partialtrack, in the operation 908 the empty portion of the partial track isassigned as a first portion of the isolation region and a correspondingportion of an adjacent trop track is assigned as a second portion of theisolation region. Alternately, if the end bottom track or top track is apartial track, the empty portion is assigned as a first portion of anisolation region and a circumferentially complementary portion of theadjacent top track or adjacent bottom track, respectively), as thesecond portion of the isolation region. If the end bottom track of theband is a full track, in an operation 910 the adjacent top track isassigned as the isolation region. Alternately, if the end bottom or toptrack is a full track, the adjacent top or bottom track, respectively,is assigned as the isolation region.

After assigning the isolation region in the operation 908 or 910, thenext band is determined, beginning with an operation 912 where sectorsof adjacent bottom tracks are supposedly filled with one band of data.This operation 912 corresponds to operation 902 which leads to thesubsequent operations, where another band is formatted and the isolationregion is assigned. The process 900 can be continued until the desirednumber of bands has been formatted, e.g., an entire disc.

FIG. 6 provides detailed guidance as to when to stop iterativesupposition, and all of FIGS. 7, 8 and 9 provide various exampleoperations for allocating disc space in the storage medium byidentifying a boundary of the first band and separating writable tracksof different bands is provided. In all processes, the practitioner isdirected to perform iterative supposition, stopping when an isolationregion can be formatted.

Referring to FIG. 10, a block diagram of a computer system 1000 suitablefor implementing one or more aspects of a system is shown. The computersystem 1000 is capable of executing a computer program product embodiedin a tangible computer-readable storage medium to execute a computerprocess. The computer process may include allocating logical sectors tostore interlaced magnetic recording bands. Data and program files may beinput to the computer system 1000, which reads the files and executesthe programs therein using one or more processors. Some of the elementsof a computer system 1000 are shown in FIG. 10 wherein a processor 1002is shown having an input/output (I/O) section 1004, a Central ProcessingUnit (CPU) 1006, and a memory section 1008. There may be one or moreprocessors 1002, such that the processor 1002 of the computing system1000 comprises a single central-processing unit 1006, or a plurality ofprocessing units. The processors may be single core or multi-coreprocessors. The computing system 1000 may be a conventional computer, adistributed computer, or any other type of computer. The describedtechnology is optionally implemented in software loaded in memory 1008,a disc storage unit 1012, and/or communicated via a wired or wirelessnetwork link 1014 on a carrier signal (e.g., Ethernet, 3G wireless, 5Gwireless, LTE (Long Term Evolution)) thereby transforming the computingsystem 1000 in FIG. 10 to a special purpose machine for implementing thedescribed operations.

The I/O section 1004 may be connected to one or more user-interfacedevices (e.g., a keyboard, a touch-screen display unit 1018, etc.) or adisc storage unit 1012. Computer program products containing mechanismsto effectuate the systems and methods in accordance with the describedtechnology may reside in the memory section 1004 or on the storage unit1012 of such a system 1000.

A communication interface 1024 is capable of connecting the computersystem 1000 to an enterprise network via the network link 1014, throughwhich the computer system can receive instructions and data embodied ina carrier wave. When used in a local area networking (LAN) environment,the computing system 1000 is connected (by wired connection orwirelessly) to a local network through the communication interface 1024,which is one type of communications device. When used in awide-area-networking (WAN) environment, the computing system 1000typically includes a modem, a network adapter, or any other type ofcommunications device for establishing communications over the wide areanetwork. In a networked environment, program modules depicted relativeto the computing system 800 or portions thereof, may be stored in aremote memory storage device. It is appreciated that the networkconnections shown are examples of communications devices for and othermeans of establishing a communications link between the computers may beused.

In an example implementation, a user interface software module, acommunication interface, an input/output interface module and othermodules may be embodied by instructions stored in memory 1008 and/or thestorage unit 1012 and executed by the processor 1002. Further, localcomputing systems, remote data sources and/or services, and otherassociated logic represent firmware, hardware, and/or software, whichmay be configured to assist in obtaining and processing media clips. Amedia clipper system may be implemented using a general purpose computerand specialized software (such as a server executing service software toa workstation or client), a special purpose computing system andspecialized software (such as a mobile device or network applianceexecuting service software), or other computing configurations. Inaddition, clipper media parameters may be stored in the memory 1008and/or the storage unit 1012 and executed by the processor 1002.

The computer system 1000 may include a variety of tangibleprocessor-readable storage media and intangible processor-readablecommunication signals. Tangible processor-readable storage can beembodied by any available media that can be accessed by the computersystem 1000 and includes both volatile and nonvolatile storage media,removable and non-removable storage media. Tangible processor-readablestorage media excludes intangible communications signals and includesvolatile and nonvolatile, removable and non-removable storage mediaimplemented in any method or technology for storage of information suchas processor-readable instructions, data structures, program modules orother data. Tangible processor-readable storage media includes, but isnot limited to, RAM, ROM, EEPROM, flash memory or other memorytechnology, CDROM, digital versatile discs (DVD) or other optical discstorage, magnetic cassettes, magnetic tape, magnetic disc storage orother magnetic storage devices, or any other tangible medium which canbe used to store the desired information and which can be accessed bythe computer system 1000. In contrast to tangible processor-readablestorage media, intangible processor-readable communication signals mayembody computer-readable instructions, data structures, program modulesor other data resident in a modulated data signal, such as a carrierwave or other signal transport mechanism. The term “modulated datasignal” means a signal that has one or more of its characteristics setor changed in such a manner as to encode information in the signal. Byway of example, and not limitation, intangible communication signalsinclude signals traveling through wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared, and other wireless media.

Thus, also provided in this disclosure is system having a storage mediumin a storage device including a plurality of bands, each band includinga plurality of tracks, each track of the plurality of tracks including anumber of sectors; and a controller. The controller is configured toexamine possible isolation regions of a first band via a process ofiterative supposition, determine an isolation region of the first band,allocate disc space in the storage medium for subsequent bands on theopposite side of the isolation region of the first band; and write onthe separately writable tracks of different bands. The controller may befurther configured to shift (during the iterative supposition) theboundary of the first band by shifting one sector at a time from abottom track to a top track, such as to fill the top track and/or emptythe bottom track. The controller may be further configured to fill thetrack adjacent to the endmost (e.g., rightmost) top track, empty theendmost (e.g., rightmost) bottom track, and add a single top track ofband isolation.

At some stage during the iterative supposition process, the endmost(e.g., rightmost) top track and bottom track are partially full.Additionally, at some states during the iterative supposition process,the endmost (e.g., rightmost) top track is full.

The implementations of the iterative supposition process describedherein are implemented as logical steps in one or more computer systems1000. The logical operations of the iterative supposition process areimplemented (1) as a sequence of processor-implemented steps executed inone or more computer systems and (2) as interconnected machine orcircuit modules within one or more computer systems. The implementationis a matter of choice, dependent on the performance requirements of thecomputer system implementing the iterative supposition process.Accordingly, the logical operations making up the iterative suppositionprocess are referred to variously as operations, steps, objects, ormodules. Furthermore, it should be understood that logical operationsmay be performed in any order, adding and omitting as desired, unlessexplicitly claimed otherwise or a specific order is inherentlynecessitated by the claim language.

The above specification and examples provide a complete description ofthe structure and use of exemplary implementations of the iterativesupposition process. Since many implementations of the iterativesupposition process can be made without departing from the spirit andscope of the invention, the invention resides in the claims hereinafterappended.

What is claimed is:
 1. A data storage formatting method comprising:filling, with supposed data, a subset of bottom tracks comprisingsectors interlaced with a subset of top tracks comprising sectors;iteratively moving supposed data from a sector of the subset of bottomtracks to a sector of the subset of top tracks until a number of emptytop tracks inward from an end non-empty bottom track is zero; andassigning an isolation region responsive to a determination that thesubset of bottom tracks has a non-full track, assigning that portion ofthe non-full track as a first portion of the isolation region, andassigning a corresponding portion of an adjacent top track as a secondportion of the isolation region, or, responsive to a determination thatthe subset of bottom tracks does not have a non-full track, assigning nomore than an entire adjacent top track as the isolation region.
 2. Themethod of claim 1, wherein prior to filling the subset of bottom tracks,determining defective sectors of the subset of bottom tracks, andfilling the sectors of the subset of bottom tracks avoiding thedefective sectors.
 3. The method of claim 1, wherein prior toiteratively moving supposed data, determining defective sectors of thesubset of top tracks, and filling the sectors of the subset of toptracks avoiding the defective sectors.
 4. The method of claim 1,comprising: filling the subset of bottom tracks left to right withsupposed data; iteratively moving and filling supposed data from asector of a right-most bottom track of the subset of bottom tracks to asector of the left-most track of the subset of top tracks, until N=0 or1, where N is the number of empty top tracks to the left of theright-most non-empty bottom track; and assigning the isolation regionresponsive to a determination if the right-most bottom track is anon-full track, assigning that portion of the non-full track as a firstportion of the isolation region, and assigning a circumferentiallycomplementary portion of an adjacent top track as a second portion ofthe isolation region.
 5. The method of claim 1, comprising: filling thesubset of bottom tracks left to right with supposed data; iterativelymoving and filling supposed data from a sector of a right-most bottomtrack of the subset of bottom tracks to a sector of the left-most trackof the subset of top tracks, until N=0 or 1, where N is the number ofempty top tracks to the left of the right-most non-empty bottom track;and assigning the isolation region responsive to a determination if theright-most bottom track is not a non-full track, assigning an adjacenttop track as the isolation region.
 6. The method of claim 1, furthercomprising after assigning an isolation region: filling a next subset ofbottom tracks with second supposed data; iteratively moving secondsupposed data from a sector of the next subset of bottom tracks to asector of a next subset of top tracks, until the number of empty toptracks inward from the end non-empty bottom track is zero; and assigninga next isolation region responsive to a determination if the next subsetof bottom tracks has a non-full track, assigning that portion of thenon-full track as a first portion of the next isolation region, andassigning a corresponding portion of an adjacent top track as a secondportion of the next isolation region, or, if the next subset of bottomtracks does not have a non-full track, assigning an adjacent top trackas the next isolation region.
 7. The method of claim 6, wherein prior tofilling the next subset of bottom tracks, determining defective sectorsof the next subset of bottom tracks, and filling the sectors of the nextsubset of bottom tracks avoiding the defective sectors.
 8. The method ofclaim 6, wherein prior to iteratively moving second supposed data,determining defective sectors of the next subset of top tracks, andfilling the sectors of the next subset of top tracks avoiding thedefective sectors.
 9. A controller for a disc drive assembly configuredto format a data storage medium of the assembly, the controllerconfigured to: fill a subset of bottom tracks comprising sectorsinterlaced with a subset of top tracks comprising sectors with supposeddata; iteratively move supposed data from a sector of the subset ofbottom tracks to a sector of the subset of top tracks, until a number ofempty top tracks inward from an end non-empty bottom track is zero; andassign an isolation region responsive to a determination that the subsetof bottom tracks has a non-full track, assign that portion of thenon-full track as a first portion of the isolation region, and assign acorresponding portion of an adjacent top track as a second portion ofthe isolation region, or if the subset of bottom tracks does not have anon-full track, assign no more than an entire adjacent top track as theisolation region.
 10. The controller of claim 9 configured to, prior tofilling the subset of bottom tracks, determine defective sectors of thesubset of bottom tracks, and fill the sectors of the subset of bottomtracks avoiding the defective sectors.
 11. The controller of claim 9configured to, prior to iteratively moving supposed data, determinedefective sectors of the subset of top tracks, and fill the sectors ofthe subset of top tracks avoiding the defective sectors.
 12. Thecontroller of claim 9 further configured to: fill the subset of bottomtracks left to right with supposed data; iteratively move and fillingsupposed data from a sector of a right-most bottom track of the subsetof bottom tracks to a sector of the right-most track of the subset oftop tracks, until N=0 or 1, where N is the number of empty top tracks tothe left of the right-most non-empty bottom track; and assign anisolation region responsive to a determination if the right-most bottomtrack is a non-full track, assign that portion of the non-full track asa first portion of the isolation region, and assign a circumferentiallycomplementary portion of an adjacent top track as a second portion ofthe isolation region.
 13. The controller of claim 9 further configuredto: fill the subset of bottom tracks left to right with supposed data;iteratively move and filling supposed data from a sector of a right-mostbottom track of the subset of bottom tracks to a sector of theright-most track of the subset of top tracks, until N=0 or 1, where N isthe number of empty top tracks to the left of the right-most non-emptybottom track; and assign an isolation region responsive to adetermination if the right-most bottom track is not a non-full track,assign an adjacent top track as the isolation region.
 14. The controllerof claim 9 further configured to, after assigning an isolation region:fill a next subset of bottom tracks with second supposed data;iteratively move second supposed data from a sector of the next subsetof bottom tracks to a sector of a next subset of top tracks, until thenumber of empty top tracks inward from the end non-empty bottom track iszero; and assign a next isolation region responsive to a determinationif the next subset of bottom tracks has a non-full track, assign thatportion of the non-full track as a first portion of the next isolationregion, and assign a corresponding portion of an adjacent top track as asecond portion of the next isolation region, or if the next subset ofbottom tracks does not have a non-full track, assign an adjacent toptrack as the next isolation region.
 15. A controller for a disc driveassembly configured to format a data storage medium of the assembly, thecontroller comprising: means to fill a subset of bottom trackscomprising sectors interlaced with a subset of top tracks comprisingsectors with supposed data; means to iteratively move supposed data froma sector of the subset of bottom tracks to a sector of the subset of toptracks, until a number of empty top tracks inward from an end non-emptybottom track is zero; and means to, responsive to a determination thatthe subset of bottom tracks has a non-full track: assign an isolationregion, assign that portion of the non-full track as a first portion ofthe isolation region, and assign a corresponding portion of an adjacenttop track as a second portion of the isolation region, or means to,responsive to a determination that the subset of bottom tracks does nothave a non-full track, assign no more than an entire adjacent top trackas the isolation region.
 16. The controller of claim 15 configured to,prior to filling the subset of bottom tracks, determine defectivesectors of the subset of bottom tracks, and fill the sectors of thesubset of bottom tracks avoiding the defective sectors.
 17. Thecontroller of claim 15 configured to, prior to iteratively movingsupposed data, determine defective sectors of the subset of top tracks,and fill the sectors of the subset of top tracks avoiding the defectivesectors.
 18. The controller of claim 15 further configured to: fill thesubset of bottom tracks left to right with supposed data; iterativelymove and filling supposed data from a sector of a right-most bottomtrack of the subset of bottom tracks to a sector of the right-most trackof the subset of top tracks, until N=0 or 1, where N is the number ofempty top tracks to the left of the right-most non-empty bottom track;and assign an isolation region responsive to a determination if theright-most bottom track is a non-full track, assign that portion of thenon-full track as a first portion of the isolation region, and assign acircumferentially complementary portion of an adjacent top track as asecond portion of the isolation region.
 19. The controller of claim 15further configured to: fill the subset of bottom tracks left to rightwith supposed data; iteratively move and filling supposed data from asector of a right-most bottom track of the subset of bottom tracks to asector of the right-most track of the subset of top tracks, until N=0 or1, where N is the number of empty top tracks to the left of theright-most non-empty bottom track; and assign an isolation regionresponsive to a determination if the right-most bottom track is not anon-full track, assign an adjacent top track as the isolation region.20. The controller of claim 15 further configured to, after assigning anisolation region: fill a next subset of bottom tracks with secondsupposed data; iteratively move second supposed data from a sector ofthe next subset of bottom tracks to a sector of a next subset of toptracks, until the number of empty top tracks inward from the endnon-empty bottom track is zero; and assign a next isolation regionresponsive to a determination if the next subset of bottom tracks has anon-full track, assign that portion of the non-full track as a firstportion of the next isolation region, and assign a corresponding portionof an adjacent top track as a second portion of the next isolationregion, or if the next subset of bottom tracks does not have a non-fulltrack, assign an adjacent top track as the next isolation region.